US5686057A - Selective oxidation of hydrogen sulfide in molten sulfur - Google Patents

Selective oxidation of hydrogen sulfide in molten sulfur Download PDF

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US5686057A
US5686057A US08/747,885 US74788596A US5686057A US 5686057 A US5686057 A US 5686057A US 74788596 A US74788596 A US 74788596A US 5686057 A US5686057 A US 5686057A
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hydrogen sulfide
sulfur
molten sulfur
hypohalide
molten
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US08/747,885
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William L. Witzig
Scott E. Lehrer
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Veolia WTS USA Inc
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BetzDearborn Inc
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Priority to EP97305478A priority patent/EP0842895A1/en
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Assigned to HISPAN CORPORATION, HERCULES INCORPORATED, BL CHEMICALS INC., BETZDEARBORN CHINA, LTD., HERCULES INVESTMENTS, LLC, HERCULES INTERNATIONAL LIMITED, BETZDEARBORN, INC., D R C LTD., FIBERVISIONS, L.L.C., BL TECHNOLOGIES, INC., COVINGTON HOLDINGS, INC., BETZDEARBORN EUROPE, INC., WSP, INC., ATHENS HOLDINGS, INC., HERCULES CHEMICAL CORPORATION, CHEMICAL TECHNOLOGIES INDIA, LTD., FIBERVISIONS PRODUCTS, INC., FIBERVISIONS INCORPORATED, HERCULES SHARED SERVICES CORPORATION, EAST BAY REALTY SERVICES, INC., HERCULES COUNTRY CLUB, INC., HERCULES INTERNATIONAL LIMITED, L.L.C., BETZDEARBORN INTERNATIONAL, INC., HERCULES EURO HOLDINGS, LLC, HERCULES CREDIT, INC., BLI HOLDING CORPORATION, HERCULES FLAVOR, INC., AQUALON COMPANY, FIBERVISIONS, L.P., HERCULES FINANCE COMPANY reassignment HISPAN CORPORATION RELEASE OF SECURITY INTEREST Assignors: BANK OF AMERICA, N.A., AS COLLATERAL AGENT
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B17/00—Sulfur; Compounds thereof
    • C01B17/02—Preparation of sulfur; Purification
    • C01B17/0243—Other after-treatment of sulfur
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B17/00—Sulfur; Compounds thereof
    • C01B17/02—Preparation of sulfur; Purification
    • C01B17/0232—Purification, e.g. degassing

Definitions

  • the present invention relates to the control of degassification of molten sulfur. More particularly, the present invention relates to the control, by selective oxidation, of the release of dissolved hydrogen sulfide from molten sulfur produced by the Claus process.
  • the present invention relates to a process for inhibiting hydrogen sulfide released from molten sulfur.
  • Elemental sulfur is produced on a commercial scale according to the Claus process in which hydrogen sulfide and oxygen react to produce elemental sulfur and water.
  • the sulfur produced is separated, in the molten form, in sulfur condensers and withdrawn for transportation or use such as in the production of sulfuric acid.
  • the adsorption rate of the gas is lower at higher temperatures.
  • the hot, molten sulfur stream in contact with a gaseous phase containing hydrogen sulfide, as found in a Claus plant should not represent a serious problem if dissolution is the only adsorption process.
  • hydrogen sulfide is known to combine with the sulfur to form hydrogen polysulfides.
  • the formation of the polysulfides is favored at the high temperatures of the Claus process. This is particularly true during the initial oxidation step in the furnace and boiler where the major portion of the sulfur is also produced.
  • the kinetics of the reverse reaction at lower temperatures characteristic of hydrogen sulfide removal are extremely slow.
  • the polysulfides are inherently produced in the Claus process, and once formed are extremely slow in decomposing. Consequently, the apparent solubility of hydrogen sulfide in liquid sulfur is unexpectedly high due to the formation of polysulfides. The subsequent release or removal is slow and difficult, frequently involving significant quantities of hydrogen sulfide being released.
  • the present inventors discovered a new method for controlling the odor and hazaards resulting from hydrogen sulfide gas evolution from molten sulfur.
  • the method of the present invention selectively oxidizes hydrogen sulfide in molten sulfur by the addition of a hypohalide such as hypochlorite.
  • the method of the present invention involves adding hypohalides to molten sulfur. It was discovered that hypohalides selectively oxidize hydrogen sulfide. The selective oxidation of hydrogen sulfide inhibits the evolution of hydrogen sulfide gas from the molten sulfur.
  • hypohalides By selective oxidation, it is meant that even in molten sulfur, where hydrogen sulfide concentrations are very low (as low as 10 ppm), the hypohalides oxidize the hydrogen sulfide preferentially over sulfur. This is evidenced by the efficacy of hypohalides in controlling hydrogen sulfide gas in the headspace over molten sulfur containing hydrogen sulfide.
  • hypochlorite a hypohalide compound
  • hypochlorite compounds are usually supplied as salts of sodium or calcium; NaOCl or Ca(OCl) 2 , respectively.
  • the addition of such salts of hypochloride to molten sulfur was found to selectively oxidize hydrogen sulfide, a relatively minor component of sulfur prepared via the Claus process. The following is a possible reaction pathway for the reaction of sodium hypochlorite with hydrogen sulfide.
  • the hypohalide of the present invention may be added in an amount ranging from about 1 to 1,000 moles hypohalide per mole of hydrogen sulfide or hydrogen polysulfide present in the system being treated.
  • the molten sulfur treated in accordance with the present invention is typically at a temperature of from about 115° C. to 450° C.
  • the hypohalide of the present invention is preferrably added continuously to molten sulfur although batchwise addition may be employed.
  • the hypohalide of the present invention may be added as an aqueous stream having a hypohalide concentration of from about 1% to 10% at a pH of from about 7-14.
  • hypochlorite solutions The resulting pH of hypochlorite solutions is between 12 and 13.
  • the ppm active shown in the above tables refers to the ppm added as concentrated sodium hypochlorite.
  • Test #4 All experiments except for Test #4 were conducted with sulfur samples collected at a Gulf Coast Refinery. Although there was significant variation in the amount of H 2 S measured in the headspace of the untreated vials, the data shows that hypochlorite is effective at inhibiting the generation of hydrogen sulfide from molten sulfur. Additionally, a comparison of hydrogen peroxide and sodium hypochlorite in Test #1, showed that hydrogen peroxide, a known scavenger of hydrogen sulfide in waste water applications, was far less effective and efficient for preventing hydrogen sulfide evolution from molten sulfur. Another oxidant, sodium perborate, was evaluated in Test #2 and found to be far less effective at preventing headspace H 2 S compared to sodium hypochlorite. Results for sodium perborate and hydrogen peroxide indicate that those oxidants may be less selective than hypochlorite as oxidants of hydrogen sulfide in a sulfur matrix.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Treating Waste Gases (AREA)

Abstract

A method for inhibiting hydrogen sulfite evolution from molten sulfur is disclosed. The method involves adding a hypohalide to molten sulfur containing hydrogen sulfite. The hypohalide, such as hypochlorite, hyprobromite, and their sodium or calcium salts inhibit the evolution of hydrogen sulfite from molten sulfur.

Description

FIELD OF THE INVENTION
The present invention relates to the control of degassification of molten sulfur. More particularly, the present invention relates to the control, by selective oxidation, of the release of dissolved hydrogen sulfide from molten sulfur produced by the Claus process.
BACKGROUND OF THE INVENTION
The present invention relates to a process for inhibiting hydrogen sulfide released from molten sulfur. Elemental sulfur is produced on a commercial scale according to the Claus process in which hydrogen sulfide and oxygen react to produce elemental sulfur and water. The sulfur produced is separated, in the molten form, in sulfur condensers and withdrawn for transportation or use such as in the production of sulfuric acid.
An inherent feature of this process is the presence, in the produced molten sulfur, of dissolved hydrogen sulfide which not only contaminates the product but also poses potential hazards in several areas. In addition to creating nuisance odors in the vicinity of molten sulfur, hydrogen sulfide may be present in such quantities as to reach toxic levels when loading and unloading the sulfur. Further, when dissolved hydrogen sulfide in molten sulfur contaminates the vapor space in storage tanks and vessels, there is a threat that the lower explosive limit of hydrogen sulfide will be reached.
Normally in a gas/liquid system the adsorption rate of the gas is lower at higher temperatures. Thus, in principle, the hot, molten sulfur stream in contact with a gaseous phase containing hydrogen sulfide, as found in a Claus plant, should not represent a serious problem if dissolution is the only adsorption process. However, hydrogen sulfide is known to combine with the sulfur to form hydrogen polysulfides. The formation of the polysulfides is favored at the high temperatures of the Claus process. This is particularly true during the initial oxidation step in the furnace and boiler where the major portion of the sulfur is also produced. Unfortunately, the kinetics of the reverse reaction at lower temperatures characteristic of hydrogen sulfide removal are extremely slow. Thus, the polysulfides are inherently produced in the Claus process, and once formed are extremely slow in decomposing. Consequently, the apparent solubility of hydrogen sulfide in liquid sulfur is unexpectedly high due to the formation of polysulfides. The subsequent release or removal is slow and difficult, frequently involving significant quantities of hydrogen sulfide being released.
In response to this problem a number of methods have been suggested or developed to remove hydrogen sulfide from molten sulfur produced by the Claus process. Release of dissolved hydrogen sulfide has been carried out by agitating the molten sulfur by various means, by providing a sulfur lift through air bubbles and by circulating the sulfur over a stripping column. Mechanical agitation has also been employed. Released hydrogen sulfide is often removed by a sweep gas such as air, Claus tail gas or nitrogen.
The use of solid catalyst to convert hydrogen polysulfide to hydrogen sulfide and removal with a purge gas containing oxygen is disclosed in U.S. Pat. No. 4,844,720. United Kingdom Patent Specification 1,433,822 discloses the use of a nitrogen containing compound and an oxidizing gas to convert hydrogen polysulfides to hydrogen sulfide which is removed from molten sulfur. Exemplary nitrogen containing compounds disclosed therein are ammonia, amines including alkylamines or hydroxyalkylamines or urea or substituted urea.
The removal of odor from air or gas streams by scrubbing with a dilute alkaline solution of sodium hypochlorite and passing the solution through a nickel-based catalyst on a ceramic matrix is disclosed by Valentin et al. in the A New Process for Controlling Effluent Treatment Odors, BHR Group Conference Series Publication (1993), Second International Conference on Advances in Water and Effluent Treatment 1993, pages 107-117.
The effects of hydrogen peroxide, sodium/calcium hypochlorite and ferrous/ferric salts on hydrogen sulphide desolved in waste water is described in Evaluation of Chemicals to Control The Generation of Malodorus Hydrogen Sulfide in Waste Water, M. Tomar and T. Abdullah, Water Resources Volume 28 No. 12, pages 2545-2552, 1994.
SUMMARY OF THE INVENTION
The present inventors discovered a new method for controlling the odor and hazaards resulting from hydrogen sulfide gas evolution from molten sulfur. The method of the present invention selectively oxidizes hydrogen sulfide in molten sulfur by the addition of a hypohalide such as hypochlorite. The method of the present invention involves adding hypohalides to molten sulfur. It was discovered that hypohalides selectively oxidize hydrogen sulfide. The selective oxidation of hydrogen sulfide inhibits the evolution of hydrogen sulfide gas from the molten sulfur. By selective oxidation, it is meant that even in molten sulfur, where hydrogen sulfide concentrations are very low (as low as 10 ppm), the hypohalides oxidize the hydrogen sulfide preferentially over sulfur. This is evidenced by the efficacy of hypohalides in controlling hydrogen sulfide gas in the headspace over molten sulfur containing hydrogen sulfide.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present inventors have discovered that the problems resulting from hydrogen sulfide gas evolution from molten sulfur could be controlled by treatment with a hypohalide. The addition of a hypohalide to molten sulfur was found to inhibit the volatilization of hydrogen sulfide gas. The preferred hypohalide is hypochlorite. It is believed that other hypohalides such as hypobromite will also provide this unexpected result. Commercially, hypochlorite compounds are usually supplied as salts of sodium or calcium; NaOCl or Ca(OCl)2, respectively. The addition of such salts of hypochloride to molten sulfur was found to selectively oxidize hydrogen sulfide, a relatively minor component of sulfur prepared via the Claus process. The following is a possible reaction pathway for the reaction of sodium hypochlorite with hydrogen sulfide.
NaOCl+H.sub.2 S→H.sub.2 O+S+NaCl
The hypohalide of the present invention may be added in an amount ranging from about 1 to 1,000 moles hypohalide per mole of hydrogen sulfide or hydrogen polysulfide present in the system being treated. The molten sulfur treated in accordance with the present invention is typically at a temperature of from about 115° C. to 450° C. The hypohalide of the present invention is preferrably added continuously to molten sulfur although batchwise addition may be employed. The hypohalide of the present invention may be added as an aqueous stream having a hypohalide concentration of from about 1% to 10% at a pH of from about 7-14.
The present invention will now be further described with reference to a number of specific examples which are intended to be illustrative and not as restricting the scope of the present invention.
Testing was conducted using a molten sulfur sample collected from a Claus unit at a Gulf Coast refinery as well as with a sample of reagent grade elemental sulfur. The sulfur was liquefied and added to vials for headspace gas chromatography. While maintaining the sulfur in the molten state, the sulfur in the vials was overpressured at 10 psig with a mixed gas containing 2000 ppm H2 S in nitrogen. The vials were placed in an oven at 138° C. for approximately 16 hours to achieve equilibration of the H2 S between the vapor and liquid phases. Treatments were added to the molten sulfur and allowed a 16 to 18 hour reaction period with the molten sulfur at 138° C. These conditions were chosen to be representative of both the temperature and residence time of sulfur in a sulfur pit.
H2 S concentrations above the molten sulfur were analyzed by gas chromatography using a detector specific for sulfur compounds. Results of these analyses are shown below for four experiments, tests 1-4.
______________________________________                                    
TEST #1                                                                   
Sulfur - Sample form Gulf Coast Refinery                                  
Untreated Headspace H.sub.2 S Average = 1020 ppm                          
ppm H.sub.2 S - Avg.                                                      
Treatment                                                                 
                5.25%   Hydrogen                                          
ppm Active      NaOCl   Peroxide                                          
______________________________________                                    
10              790     911                                               
25              209     1045                                              
50              11      911                                               
100             <15     649                                               
250             16      274                                               
______________________________________                                    

______________________________________                                    
TEST #2                                                                   
Sulfur - Sample from Gulf Coast Refinery                                  
Untreated Headspace H.sub.2 S Average - 798 ppm                           
Sodium Perborate                                                          
5% in H.sub.2 O                                                           
ppm Active    ppm H.sub.2 S - Average                                     
______________________________________                                    
10            828                                                         
25            363                                                         
50            174                                                         
100           138                                                         
______________________________________                                    

______________________________________                                    
TEST #3                                                                   
Sulfur - Sample from Gulf Coast Refinery                                  
Untreated Headspace H.sub.2 S Average - 360 ppm                           
ppm H.sub.2 S - Avg.                                                      
Treatment                                                                 
               12.5%                                                      
       ppm Active                                                         
               NaOCl                                                      
______________________________________                                    
       10      <50                                                        
       20      <50                                                        
       30      48                                                         
       40      <50                                                        
       50      <50                                                        
       70      <50                                                        
______________________________________                                    

______________________________________                                    
TEST #4                                                                   
Sulfur - Reagent Grade Elemental Sulfur                                   
Untreated Headspace H.sub.2 S Average = 320                               
ppm H.sub.2 S - Avg.                                                      
Treatment                                                                 
               12.5%                                                      
       ppm Active                                                         
               NaOCl                                                      
______________________________________                                    
       2       380                                                        
       5       190                                                        
       10      240                                                        
       20      <50                                                        
       30      60                                                         
       60      <50                                                        
______________________________________
The resulting pH of hypochlorite solutions is between 12 and 13. In all tests of hypochlorite, the ppm active shown in the above tables refers to the ppm added as concentrated sodium hypochlorite.
All experiments except for Test #4 were conducted with sulfur samples collected at a Gulf Coast Refinery. Although there was significant variation in the amount of H2 S measured in the headspace of the untreated vials, the data shows that hypochlorite is effective at inhibiting the generation of hydrogen sulfide from molten sulfur. Additionally, a comparison of hydrogen peroxide and sodium hypochlorite in Test #1, showed that hydrogen peroxide, a known scavenger of hydrogen sulfide in waste water applications, was far less effective and efficient for preventing hydrogen sulfide evolution from molten sulfur. Another oxidant, sodium perborate, was evaluated in Test #2 and found to be far less effective at preventing headspace H2 S compared to sodium hypochlorite. Results for sodium perborate and hydrogen peroxide indicate that those oxidants may be less selective than hypochlorite as oxidants of hydrogen sulfide in a sulfur matrix.
While this invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of the invention will be obvious to those skilled in the art. The appended claims and this invention should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention.

Claims (3)

What is claimed is:
1. A method of inhibiting hydrogen sulfide evolution from molten sulfur comprising adding to molten sulfur a hypohalide in an amount of from about 1 to 1,000 moles hypohalide per mole of hydrogen sulfide, hydrogen polysulfide and combinations thereof present in said molten sulfur.
2. The method of claim 1 wherein said hypohalide is selected from the group consisting of hypochlorite and hypobromite.
3. The method of claim 1 wherein said hypohalide is added to said molten sulfur in the form of a sodium or calcium salt.
US08/747,885 1996-11-13 1996-11-13 Selective oxidation of hydrogen sulfide in molten sulfur Expired - Fee Related US5686057A (en)

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EP97305478A EP0842895A1 (en) 1996-11-13 1997-07-22 Selective oxidation of hydrogen sulfide in molten sulfur
CA002211399A CA2211399C (en) 1996-11-13 1997-08-08 Selective oxidation of hydrogen sulfide in molten sulfur

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6656445B2 (en) 2000-10-13 2003-12-02 Baker Hughes Incorporated Hydrogen sulfide abatement in molten sulfur
US20080175778A1 (en) * 2002-09-26 2008-07-24 Evonik Degussa Gmbh Process for the conversion of polysulfanes

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3413841A1 (en) 2016-02-09 2018-12-19 AMO Groningen B.V. Progressive power intraocular lens, and methods of use and manufacture

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GB346835A (en) * 1930-01-18 1931-04-20 Ig Farbenindustrie Ag Improvements in the purification of sulphur
US3278269A (en) * 1963-08-13 1966-10-11 Freeport Sulphur Co Sulphur treatment
US3619143A (en) * 1968-04-23 1971-11-09 Auxiliar Ind Sa Empresa Process for the purification of sulfur from pyrite and other sulfur-containing ores
GB1433822A (en) * 1972-05-24 1976-04-28 Shell Int Research Process for the removal of hydrogen sulphide from molten sulphur
US4256728A (en) * 1978-10-11 1981-03-17 Takeda Chemical Industries, Ltd. Deodorization method
US4844720A (en) * 1982-04-02 1989-07-04 Amoco Corporation Process for removal of hydrogen sulfide and hydrogen polysulfide from liquid sulfur
US5080695A (en) * 1990-10-12 1992-01-14 Marathon Oil Company Method of removing hydrogen sulfide from liquid sulfur

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FR2601350B1 (en) * 1986-07-10 1988-09-30 Elf Aquitaine PROCESS FOR THE RAPID REMOVAL OF SULFURATED HYDROGEN CONTAINED IN LIQUID SULFUR AND CATALYST SYSTEM FOR USE IN ITS IMPLEMENTATION

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GB346835A (en) * 1930-01-18 1931-04-20 Ig Farbenindustrie Ag Improvements in the purification of sulphur
US3278269A (en) * 1963-08-13 1966-10-11 Freeport Sulphur Co Sulphur treatment
US3619143A (en) * 1968-04-23 1971-11-09 Auxiliar Ind Sa Empresa Process for the purification of sulfur from pyrite and other sulfur-containing ores
GB1433822A (en) * 1972-05-24 1976-04-28 Shell Int Research Process for the removal of hydrogen sulphide from molten sulphur
US4256728A (en) * 1978-10-11 1981-03-17 Takeda Chemical Industries, Ltd. Deodorization method
US4844720A (en) * 1982-04-02 1989-07-04 Amoco Corporation Process for removal of hydrogen sulfide and hydrogen polysulfide from liquid sulfur
US5080695A (en) * 1990-10-12 1992-01-14 Marathon Oil Company Method of removing hydrogen sulfide from liquid sulfur

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Title
A New Process for Controlling Effluent Treatment Odours: Valentin,F.H.H.; BHR Group Conference Series Publication(1993) No Month, Second International Conference on Advances in Water and Effluent Treatment, 107 117. *
A New Process for Controlling Effluent Treatment Odours: Valentin,F.H.H.; BHR Group Conference Series Publication(1993) No Month, Second International Conference on Advances in Water and Effluent Treatment, 107-117.
Evaluation of Chemicals to Control The Generation of Malodorous Hydrogen Sulfide In Waste Water: Tomar, M. and Adbdullah, T.; Water Resources, vol. 28, No. 12, pp. 2545 2552, 1994 (No Month). *
Evaluation of Chemicals to Control The Generation of Malodorous Hydrogen Sulfide In Waste Water: Tomar, M. and Adbdullah, T.; Water Resources, vol. 28, No. 12, pp. 2545-2552, 1994 (No Month).
Liquid Catalyst Efficiently Removes H2S From Liquid Sulfur: Nougayrede, J. and Voirin, R.; Oil & Gas Journal, Jul. 17, 1989, pp. 65 69. *
Liquid Catalyst Efficiently Removes H2S From Liquid Sulfur: Nougayrede, J. and Voirin, R.; Oil & Gas Journal, Jul. 17, 1989, pp. 65-69.

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6656445B2 (en) 2000-10-13 2003-12-02 Baker Hughes Incorporated Hydrogen sulfide abatement in molten sulfur
US20040086443A1 (en) * 2000-10-13 2004-05-06 Schield John A. Hydrogen sulfide abatement in molten sulfur
US6887447B2 (en) 2000-10-13 2005-05-03 Baker Hughes Incorporated Hydrogen sulfide abatement in molten sulfur
US20080175778A1 (en) * 2002-09-26 2008-07-24 Evonik Degussa Gmbh Process for the conversion of polysulfanes
US7604788B2 (en) * 2002-09-26 2009-10-20 Evonik Degussa Gmbh Process for the conversion of polysulfanes

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CA2211399A1 (en) 1998-05-13
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